7 Roci siltice si argiloase. Mineralogia argilelor, sistematica, petrogeneza

Transcription

1 7 Roci siltice si argiloase. Mineralogia argilelor, sistematica, petrogeneza

2 Argila = termenul petrografic atribuit oricarui depozit alcatuit preponderent din minerale argiloase (peste 60%) si, de regula, din fractie lutitica. Volumetric abundances of sedimentary rocks in Earth s continental crust Bridge si Demico, (2008)

3 Textura dimensiunea particulelor Structuri- laminatie, stratificatie Mineralogie Sistematica Petrogeneza

4 Gravel Gravel Folk (1974) 80% Sandy Gravel Gravel % Muddy Gravel Muddy Sandy Gravel 30% Gravelly Mud Gravelly Muddy Sand Gravelly Sand Mud Trace 5% Slightly Gravelly Mud Slightly Gravelly Sandy Mud Slightly Gravelly Muddy Sand Mud Sandy Mud Muddy Sand 1:9 Sand:Mud Ratio 1:1 9:1 Slightly Gravelly Sand Sand Sand

5 Gresii 90% Sand Sand NOTE Gravel is also present in this sample Folk (1974) Sand % Clayey Sand Muddy Sand Silty Sand 50% Sandy Clay Sandy Mud Sandy Silt 10% Clay Clay Mud Silt 1:2 2:1 Silt:Clay Ratio Silt

6 Forma particulelor - aplatizata Min. argiloase Qz Electron microscope photograph of a mudstone containing various-sized grains of quartz (blocky) and clay minerals (flaky). Photograph courtesy of David Krinsley.

7 Electron micrograph of kaolinite clayminerals magnified Note the platy or flaky appearance of the pseudohexagonal kaolinite crystals, which are arranged in this specimen in distinct books. Boggs, 2009

8 Textura dimensiunea particulelor Structuri- laminatie, stratificatie Mineralogie Sistematica Petrogeneza

9 Microfabric dependent de proprietatile mineralelor argioase Particule: - agregate - floculate/defloculate - disperse Kinds and terminology of particle associations in clay suspensions: (A) dispersed and deflocculated, (B) aggregated but deflocculated (face-to-face association, or parallel or oriented aggregation), (C) edge-to-face flocculated but dispersed, (D) edge-toedge flocculated but dispersed, (E) edge-to-face flocculated and aggregated, (F) edge-to-edge flocculated and aggregated, (G) edge to-face and edge-to-edge flocculated and aggregated. (From van Olphen, H., 1977, An Introduction to Clay Colloid Chemistry, 2nd edn.: JohnWiley and Sons, New York, NY, Fig. 23, p. 97: reprinted by permission.)

10 Schematic representation of major microstructural changes that occur in clay sediments during deposition and lithification. (From Moon, C. F. and C.W. Hurst, 1984, Fabrics of muds and shales: an overview, in Stow, D. A.V. and D. J.W. Piper, (eds.), Fine-Grained Sediments: Deep-Water Processes and Facies: Blackwell Scientific, Oxford. Fig. 5, p. 588, reprinted by permission.)

11 Stratification and parting in shales Source: Potter, P. E., et al., 1980, Sedimentology of Shale, Table 1.3, p. 16, reprinted by permission of Springer-Verlag, Berlin.

12 Shales - argile laminate Mudstone argile masive

13 Textura dimensiunea particulelor Structuri- laminatie, stratificatie Mineralogie Sistematica Petrogeneza

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19 Shale colors as related to content of organic carbon and oxidation state of iron. m represents the number of moles of iron per gram of rock. From Potter et al Copyright 1980 Springer-Verlag.

20 Textura dimensiunea particulelor Structuri- laminatie, stratificatie Mineralogie Sistematica Petrogeneza

21 A. precipitate Criteriul Petrogenetic Mineralogic Structural Textural A. reziduale A. oligomictice: A. masive Clay (caolinite, illite) (mudstone) Mud A. sedimentate Sandy Clay A. laminate A. polimictice: A. diagenetice (shale) Sandy Mud varietati feruginoase, fosfatice, silicioase, etc.

22 Textura dimensiunea particulelor Structuri- laminatie, stratificatie Mineralogie Sistematica Petrogeneza

23 Argile reziduale- alterarea Dizolvare=solubilizarea mineralelor in apa Proceselele altararii: Oxidare=mineralele reactioneaza cu oxigenul Hidroliza=mineralele reactioneaza cu apa

24 Alterarea chimica si formarea solurilor. Un profil ideal de sol Acumularea substantelor organice Descompunerea bacteriana a s.o. Alterarea chimica a mineralelor formate in B sau C Eluvierea (inlaturarea) argilei si a sarurilor Orizont bogat in s.o. si sarac in argila Iluvierea (acumularea) argilelor si a oxizilor din A Alterarea chimica a mineralelor formate in C sau parentale Orizont bogat in argila si oxizi de fier Alterarea chimica a mineralelor din rocile parentale Dezagregarea mecanica a rocilor parentale Orizont slab alterat = scoarta de alterare Roca parentala

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26 Illite zone temperate Clorite- zone temperate, aride Montmorilonit- zone temperate, aride, umede Caolinit-zone tropicale

27 Dependenta de climat a solurilor Climat rece (polar/alpin) Climat temperat Climat ariddesertic Evaporarea Climat moderat cald-umed Climat tropical + Caolinit Smectit + Illit Caliche Roca slab alterata Soluri bune pentru agricultura Roca nealterata

28 Argile transportate

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30 Fraction analysis of Mississippi alluvial mud from levee bank on the east side of New Madrid Bend, 25-A-I, Fulton Co.. Kentucky. From Potter et al., Copyright 1975 Elf-Aquitiane.

31 Plots showing the average mineral composition of a series of recent mud samples from the vicinity of the Mississippi River delta. From Shaw and Waver Copyright 1965 SOC. Econ. Paleo.Miner.

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33 Scaderea porozitatii proportional cu adancimea de ingropare (Hinch, 1978)

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